Hyphens and dashes

There are several different types of punctuation that fall under the category of dashes and hyphens, and they all look basically the same: like a straight line. The only difference between them is the length of the line, but each type of hyphen and dash serves a distinct purpose.

Hyphen (-)

The hyphen is the shortest of these punctuation marks. When you hit the minus key on the keyboard, you're typing a hyphen.

Breaking up a word

Hyphens are used to indicate that a word has been broken between two lines. If you're going to break up a word, it should be done between syllables, and the word should be split roughly evenly.

Correct

We went to the lecture at the museum just for enter-tainment, but we learned a lot.

Incorrect

We went to the lecture at the museum just for enterta-inment, but we learned a lot.

We went to the lecture at the museum just for ent-ertainmain, but we learned a lot.

If the word already contains a hyphen, then it should be split at that hyphen.

Correct

We couldn't stand our neighbor: she was so bossy and self-important.

Incorrect

We couldn't stand our neighbor: she was so bossy and self-impor-tant.

Most word processors will have a setting that allows you to automatically split words at the end of a line. Style guides differ on whether to split words or leave them whole, but most guides today will advise not to split words. Check with your teacher if you're unsure.

Joining two words to form an adjective

Hyphens are also used to join two words that function as a single adjective when they're placed before the noun they modify, for example "ten-minute walk" and "high-class party." If you're confused about whether two words form a compound adjective, just ask if it would make sense to use them separately. It doesn't make sense to say a "ten walk" or a "minute walk." If the words need to be together for them to make sense, then they need a hyphen. There is no white space on either side of the hyphen.

Correct

The well-spoken man was chosen by the group to lead their presentation.

Incorrect

The well spoken man was chosen by the group to lead their presentation.

However, when the adjectives come after the noun they are not hyphenated.

Correct

The man was well spoken.

Incorrect

The man was well-spoken.

Before prefixes

Hyphens are used after the prefixes ex, self, and all and after prefixes that come before a capitalized noun or a number.

Forming compound numbers

Use a hyphen when writing out compound numbers (numbers made up of two words). These are the numbers between 22 and 99. Numbers over 99 won't require hyphens.

Correct

forty-seven; one hundred sixty-six

Incorrect

forty seven; one-hundred-sixty-six; one hundred-sixty-six; one hundred sixty six

En dash (–)

The en dash (so-called because it's roughly the width of the letter n) is slightly longer than a hyphen. In most word processors, you can make an en dash by holding down the alt key and typing the numbers 0150.

Ranges

En dashes are used to indicate ranges of inclusive numbers or dates.

Correct

1995–1997; January–March; 6:00 A.M.–4:00 P.M.

Complex compound adjectives

An en dash is used instead of a hyphen when forming a compound adjective from words that already have a white space (like New York) or a hyphen (such as talked-about).

Em dash (—)

Em dashes are longer than en dashes or hyphens (they're roughly the length of the letter m). You can type an em dash by holding down the alt key and typing 0151. In Word, if you type two hyphens with text on either side, the program will automatically insert an em dash.

Em dashes are not commonly used in formal writing, but in informal writing they are used in the place of commas, colons, or parenthesis to set apart text. No white space is left on either side. They usually indicate emphasis or a change in thought.

Correct

My friends—that is, my former friends—ganged up on me

I understand what you mean—you don't want me to go to the party.

In formal writing, em dashes can usually be replaced with other punctuation.

Correct

My friends, that is, my former friends, ganged up on me.

I understand what you mean: you don't want me to go to the party.

Brackets

Parenthesis ()

Parenthesis are used to set apart words or phrases that could be left out of a sentence without altering its meaning. Usually it's information that is not central to the main idea but is instead added as an aside to the reader.

Correct

The girls (all from the same class) arrived at the party together.

Punctuation within parenthesis should stand alone, and punctuation for the outside sentence should be outside the parenthesis.

Correct

At the end of the day, we all knew who was responsible (Alan).

I called him earlier (I know, I shouldn't have!), but he didn't answer.

Note that the sentences are still complete without the parenthesis: "The girls arrived at the party together" and "I called him earlier, but he didn't answer."

When you put something in parenthesis, you're telling the reader that it's not vital information, so be careful how you use them. If you want to set apart certain parts of sentence without making them seem less important, you can often use commas or colons.

Correct

The girls, who were all from the same class, arrived at the party together.

At the end of the day, we all knew who was responsible: Alan.

Parenthesis can either be inserted into a sentence, as in the examples above, or they can stand alone. When the parenthesis enclose a complete sentence, the punctuation is included inside the parenthesis.

Correct

We arranged to meet them for dinner at eight. (We knew they'd be early, though, so we left the house at seven.)

Parenthesis also have several specific functions in formal writing, for example to indicate that a noun can be singular or plural or to add supplementary information after a name:

Correct

the chair(s); Jackson (D., Texas)

Brackets []

Changing a quote

Square brackets are used to indicate that a quote has been altered, usually because the author has needed to add text to clarify what is being quoted or to make the tense fit within the larger paper.

Correct

"It [the ring] was her most expensive possession." (clarifying what "it" is)

"The new edition [see Chapter 2] will be released in June." (giving direction to the reader)